The present invention relates to a method for organizing the execution of electronically controlled switching processes. More particularly, the invention relates to such a method for organizing the execution of electronically controlled switching processes in which sequential and/or parallel steps are activated by preset transition conditions and are deactivated by advancement of the execution beyond that step. In addition, the present invention relates to a software tool that is suitable for carrying out the method, and, furthermore, to a programming device having a software tool of this type.
The organization of sequence control systems is typically preset via corresponding programming in a programming device. The switching procedures in these sequence control systems, referred to here in simplified form as executions, are carried out using various actuators, for instance also including evaluation of sensor data. A process to be controlled is displayed graphically and additionally embodied in programming form in the programming device or personal computer through corresponding function and data models. The processing aspects are of central importance, in particular, in the function model and thus form network nodes.
The data streams are controlled by control data or events. While the network nodes may be refined and used for displaying even complex processes, however, an array of boundary conditions must be maintained in order to ensure conformity to the actual processes. The sequence control systems may also be represented, in a manner known per se as Petri networks. Petri networks evince strict formalization, may be represented graphically and also analytically, and can easily be made accessible to processing by the programming device. These representations based on Petri networks are, for example, described in Industry Standard DIN EN 61131 and are essentially formed by groups of steps and transitions (advancement conditions), which can be linked and/or marked with directed connections. Herein, each step is composed of individual actions and each transition has a transition condition.
Both parallel and sequential executions of the control system can be described using the known Petri networks, this methodology also permitting individual locations of the network, and therefore also steps of the sequence control system, to be marked multiple times. However, this does not typically make sense from the viewpoint of sequence control, this being true not only for the same step, but even for steps lying one after another in linear sections. This means that, even though branching to parallel executions is admissible, this parallelism is absolutely required to be brought back orderly together, since a change to a parallel execution is inadmissible per se.
The present invention therefore has an object of providing a method for organizing the execution of electronically controlled switching processes, in which it is ensured that only admissible network states are achieved in a sequence control system. In addition, a software tool for carrying out the method is to be provided.
According to one formulation of the invention, these and other objects are solved by a method for organizing the execution of electronically controlled switching procedures, in which sequential and/or parallel steps are activated by preset transition conditions and are deactivated by the advancement of the execution, and in which, advantageously, inadmissible parallel steps are deactivated during the activation of a step, wherein the respective inadmissible steps were previously recorded in a stored matrix. Software tools and programming devices utilizing the inventive method are also encompassed by the present invention.
The activation of steps that potentially lead to inadmissible combinations arises due to, for example, an inadmissible graphic transition in the execution plan, an external activation, or an activation through step activity. To resolve the situation, an intervention by hand, for example, is first and foremost considered, i.e., the operator on the machine to be controlled gives the explicit signal to activate a specific step. However, depending on the capabilities of the programming system on which the electronic data processing is based, this may also be performed by a pinpointed activation as an activity of another step.
It may be possible to recognize potential conflict situations during the activation of the steps in the graphic of the execution plan at the time this plan is drawn up. However, this is neither sufficiently reliable nor absolutely necessary for most applications. For one thing, a graphic transition of this type does not automatically have to occur dynamically at a time at which this parallel branch is occupied, so to speak. Furthermore, the error situation may arise even in graphics that are free of conflict by way of the external intervention possibilities described above.
The methods and systems according to the present invention are advantageous above all because parallelism in the execution plan does not have to be dispensed with entirely, as was sometimes necessary up to now. It is also no longer necessary to protect the machines to be controlled in such a way that they react good-naturedly to the conflicts arising.
These and further features according to the preferred refinements of the present invention are disclosed not only by way of the claims but also from the description and the drawings. The individual features and aspects of the invention are capable of being implemented alone or jointly, e.g. in the form of sub-combinations of the preferred embodiments of the present invention. These features and aspects of the invention are also capable of being utilized in other fields and provide advantageous embodiments which are within the scope of the present invention in their own right and for which protection is sought.